[unreadable] Characterizing angiogenesis and microvascular architecture in biological systems is of tremendous value in a wide range of biological fields such as tissue engineering, cancer, rehumatoid arthritis, and ischemic heart disease research. The ability to perform such characterizations efficiently and effectively is hindered, in large part, by the available imaging modalities. The development of accurate three-dimensional (3D) methods for imaging microvascular structure represents a fundamentally important and technically challenging problem, whose solution would facilitate important advancements in biomedical science. Recently there have been exciting advancements in coherent X-ray sources and imaging hardware that have permitted for the development of novel X-ray phase-contrast imaging techniques that may be ideally suited for imaging microvascular structure. However, there remains a great need for the development of tomographic reconstruction algorithms that can produce accurate image reconstructions. The broad objective of this proposal is to utilize a recently proposed intensity diffraction tomography (I-DT) reconstruction theory to develop and investigate reconstruction algorithms for in-line X-ray phase-contrast microtomography, and evaluate their use for reconstructing the microvascular structure of biological tissues. The specific aims of the research are: (1) To investigate I-DT reconstruction algorithms for phase-contrast tomography, (2) To develop and investigate novel reconstruction algorithms for phase-contrast tomography, (3) To reconstruct 3D images of microvascular structure from experimental data, and (4) To evaluate quantitatively the reconstructed 3D microvascular structure. The successful completion of our proposed research will establish in-line phase-contrast tomography as an effective and important modality for imaging microvascular structure. [unreadable] [unreadable]